body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-color: #333;
    font-family: 'Arial', sans-serif;
}

.calculator {
    width: 320px;
    border: 1px solid #444;
    border-radius: 20px;
    padding: 20px;
    background-color: #000;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.5);
}

.display {
    font-size: 2.5em;
    margin-bottom: 20px;
    padding: 20px;
    background-color: #333;
    color: #fff;
    text-align: right;
    border-radius: 10px;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

.button {
    padding: 20px;
    font-size: 1.5em;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    transition: background-color 0.3s;
}

.button.digit {
    background-color: #505050;
    color: #fff;
}

.button.operator {
    background-color: #ff9500;
    color: #fff;
}

.button.function {
    background-color: #a5a5a5;
    color: #000;
}

.button.zero {
    grid-column: span 2;
    border-radius: 25px;
}

.button:hover {
    filter: brightness(1.2);
}

.button.operator:hover {
    background-color: #ff7f0a;
}